Most internal combustion engines utilize a rotating camshaft to open and close intake valves, exhaust valves, and sometimes actuate fuel injectors at precise timings for each of a plurality of engine cylinders. Most engines so equipped utilize one or more journal bearings to rotationally support the camshaft during rotation, and a pair of thrust bearing surfaces to limit movement of the camshaft along its axis of rotation. In some instances, such as that taught in U.S. Pat. No. 6,786,643, the camshaft includes an integrally formed disc that is trapped within a slot defined by the engine housing to prevent the camshaft from moving beyond where the disc contacts the side walls of the slot during normal engine operation. In other instances, the camshaft itself might define an annular groove that receives a protrusion defined by the engine housing that prevents movement of the camshaft along its axis of rotation by interaction between the housing protrusion and the side walls of the annular slot defined by the camshaft. In still another strategy, taught in U.S. Pat. No. 5,826,461, a first thrust bearing surface may be located on one side of a disc integrally formed on a collar that is interference fit on the outside of the camshaft, and an opposite thrust bearing surface is located on an adjacent inner surface of a cam gear mounted to one end of the camshaft. The two thrust bearing surfaces define an annular slot that receives a portion of the engine housing, thus preventing movement of the camshaft beyond where the thrust bearing surfaces contact their counterpart thrust surfaces of the engine housing. While these and likely other thrust bearing strategies are known and available, they often suffer drawbacks associated with manufacturing complexity, cost, extra components, and even sometimes undesirable weakening of the camshaft in order to accommodate thrust bearing surfaces.
In another aspect of engine design, it is well known that many moving parts in and on the engine need continuous lubrication in order for the engine to function properly for an expected working life. In typical situations, a lubrication pump circulates lubrication oil to a number of engine galleries, that in turn supply individual lubrication jets associated with lifters, pistons, connecting rods, crank bearings, cam bearings, etc. Because these lubrication galleries are sometimes arranged in parallel, and because the lubricating demands associated with different lubrication galleries may not be equal, it is possible that excess lubrication fluid may flow to and through one lubrication gallery leaving a deficit, and potentially less than adequate lubrication, for the components associated with a different lubrication gallery. Finding strategies to insure that all of the lubrication galleries receive an adequate supply of lubricating oil can sometimes be problematic and elusive.
The present disclosure is directed to one or more of the problems set forth above.